This invention is an occlusive device, and typically includes a substrate, often a helical metal coil, and a multiplicity of fibers incorporated therewith for enhancing a tissue-ingrowth response for occlusion.
We use the term "occlusive devices" to encompass devices for occluding vascular lumens as well as any other body cavities requiring occlusion to carry out a medical treatment. We use the term "vaso-occlusion devices" to encompass devices used in endovascular applications, such as in occluding veins, arteries, fistulas, or aneurysms. Although the invention is described largely in terms of vaso-occlusion devices, we intend the present invention to include the wider scope of occlusion devices.
Vaso-occlusion devices of the prior art have been associated with two pertinent limitations.
First, fibers for enhancing the thrombogenicity of vaso-occlusion devices must be securely attached to an underlying substrate, usually a coil, of the device. Without being secured, detachment of the fibers from the substrate coil could cause embolization at some remote, undesired site in the vasculature.
Second, vaso-occlusion devices are re-deployed through conduit delivery tubes (e.g., catheters or sheaths), often to sites in distant tortuous portions of the anatomy. Such delivery tubes often fit closely over the occlusive device. Such a fit may become tight upon any ovalization of the delivery tube in tight bends of a distal tortuous lumen. The presence of fibers extending from the vasoocclusive device and the orientation that those fibers take can add a significant frictional component during the deployment of the device through the delivery tube. Friction due to the fibers becomes more of a problem when larger coils are employed and when distal, tortuous anatomy must be negotiated.
The shape of the occlusive devices determines the overall profile of the delivery system and resultant negotiability of the system in the anatomy. The delivery system profile, in turn, affects patient morbidity. Thus, larger coil substrates present a more difficult problem in terms of accommodating fibers in the intraluminal space with the delivery conduit tube. One way of meeting such a challenge is shown in Castaneda-Zuniga, et al., in "A New Device for the Safe Delivery of Stainless Steel Coils," Radiology 136:230-231. This document suggests that delivery of coils to larger arteries requires large-bore TEFLON-lined catheters in order to decrease the friction that occurs as the coil is introduced.
Where tortuous anatomy must be negotiated, the conduit delivery tube lumen often assumes an oval cross section (i.e., it becomes "ovalized") within a turn and effectively narrows the lumen. Here, as well, the ability to accommodate the thrombogenic fibers on substrate coils of occlusion devices becomes more limited.
The following documents are typical descriptions of various implantable devices having attached fibers.
U.S. Pat. No. 5,256,146, to Ensminger et al., discloses an implantable vascular catheterization system for maintaining the tip of an implanted catheter at a desired position within a blood vessel. The disclosure describes a device having an anchoring filament with "clotting means" attached. These clotting means may be numerous filaments of a textile material or `fuzz` intended to cause the blood vessel in the anchoring area become occluded due to blood clotting. No technique for attaching the fibers is shown nor are any particular orientation of the fibers described.
U.S. Pat. No. 5,382,260, to Dormandy, teaches an embolization device made up of a metal coil with fibers. Each group of fibers has an intermediate portion looped about one central turn of the coil. The ends of the fibers extend interiorly of the coil and outwardly of the coil through the spaces between two adjacent turns that are adjacent the central turn. The ends of the fibers are free to move. The loop serves as the sole means for retaining the group of fibers on the coil.
The ends of the group of fibers extend radially from the coil at the same position. They are said to be spaced extremely close along the longitudinal axis, with multiple fibers bundles spaced a "suitable distance" apart. This configuration focuses a frictional component on one side of the catheter. The closeness and overall quantity of fibers that can be placed on the coil is therefore limited by the increased friction from concentrated fiber bundles in the intraluminal space on substantially one side of the coil. The "suitable distance" that multiple fibers must be spaced apart is largely determined by the frictional resistance limitation through the delivery tube attributable to the fibers in the disclosed orientation.
U.S. Pat. No. 5,304,194 to Chee, the disclosure from which is herein incorporated by reference, discloses a vaso-occlusive device having a metal coil with at least one fibrous element attached to its proximal end. The fibrous element extends in a sinusoidal wave that loops about individual windings at intervals spaced along the axis of the coil. Chee teaches that a method for attaching the fibrous element is tying a knot to secure the end of the fiber onto the coil. Chee further teaches that knotting at the ends is desirable, but not essential, since threading of the loops about the windings is sufficient to anchor the bundle to the coil.
Since Chee teaches the use of loops of fiber extending from the coil substrate having successive loops oriented longitudinally along the substrate coil, the fibers of the have a relatively constant radial aspect on the coil substrate.
Although Chee also teaches the use of fibers on opposite radial sides of the coil, a different fiber is present on each of the two opposing radial positions. Also, the fibers of this embodiment form loops external to the coil. The embodiment requires looping the fiber on one side of the coil substantially on the same coil windings as where the fiber on the opposite coil side is looped to avoid effectively tying the opposite loop down upon the coil.
U.S. Pat. No. 4,820,298, to Leveen et al., discloses a device for sealing off the dilated portion of a vascular aneurysm. Leveen et al discloses a flexible tubular body formed from a medical thermoplastic in the form of a helix. The helical loops of the flexible tubular body are connected to strands which extend into the space defined by each coil of the helix to allow clot formation and ingrowth of tissue. Leveen teaches interfacing the strands with the coils by mounting or integrally forming them with the tubular substrate body. Such mounting or integral forming is said to be accomplished through the use of sonic welding or adhesives.
U.S. Pat. No. 5,382,259, to Phelps, teaches a vasoocclusion coil onto which a fibrous, woven, or braided tubular covering or element is placed co-axially to an underlying substrate by melting, fusing, or gluing the covering to at least one end of the substrate. The substrate is typically a braid or coil. This device is described as presenting a high ratio of fibrous material to metallic material and as being easily placed within the body's vasculature.
U.S. Pat. No. 3,687,129, to Nuwayser, teaches a male contraceptive device comprising a plug with a very fine layer of flock or coating of fabric on its outer walls. Nuwayser teaches that the fabric web may be heat bonded in mats to a sheet of polymer. The polymer is heated with gradually rising temperature until the polymer surface is softened, and the fabric is then impressed on the soft surface with an embossed press to ensure the formation of cell-entrapping loops. The disclosure states that the bonding technique is enhanced by using a substrate polymer whose melting point is lower than the fabric material.
The device described in Nuwayser is a hollow plug said to be suitable as a vas deferens occluding device. The device has a fabric lining on its interior surface similar to that fabric taught for the outer surface. Bonding techniques taught for the outer fabric are also taught for the interior fabric.
None of the cited references teaches a device for occluding body lumens or cavities having fibers secured to a substrate with free fiber ends extending outwardly from the occlusion device at radially spaced locations on the substrate when deployed in-vivo where the free ends orient longitudinally in the intra-luminal space when the device is delivered through a delivery sheath and consequently parallel to the friction plane to enhance co-axial delivery.
None of the references teach heating an interface between thrombogenic fibers and vaso-occlusive substrates to cause localized deformation in at least one of said substrate or fibers, securing the fibers to the substrate in a desired orientation for enhanced thrombogenesis and co-axial delivery to distal anatomy.